TORONTO - A B.C. producer of medical marijuana has voluntarily recalled a batch of its "purple kush" strain and is advising consumers not to smoke the weed after a Health Canada inspection of the grower's operations turned up "issues" with its production practices.

In what is believed to be the first recall of medical cannabis in Canada, Greenleaf Medicinals of Nanaimo, B.C., is advising clients to immediately stop using any marijuana they still possess from batch number PK-10-20-13.

"Following an inspection at Greenleaf Medicinals, Health Canada inspectors identified issues with processes that affect quality control, good production practices and oversight," a spokesman for the federal department said late Tuesday by email.

"This includes potential residues from use of unregistered pesticides, unsanitary production conditions, concerns with testing standards and/or control of plant materials."

Health Canada did not say what adverse effects might occur from smoking or ingesting the recalled pot.

Greenleaf could not be reached for comment; its website appears to have been taken down and the company's name does not appear on Health Canada's online list of authorized growers of medical marijuana.

The Health Canada spokesman said Greenleaf has been temporarily removed from the list until its production problems have been corrected and its operations re-inspected.

The company has told Health Canada it is working with other licensed producers to find a supply of marijuana for 63 clients affected by the recall of its purple kush, a potent strain of cannabis that contains a high concentration of the psychoactive ingredient THC.

Greenleaf has advised customers to return the product to the company via a secure courier.

If clients instead choose to destroy the product, they should add water to the dried marijuana to render it unusable, mix it with cat litter to mask the odour and dispose of it with regular household waste.

About a dozen producers have been licensed by Health Canada to sell various strains of medicinal marijuana after the federal government revamped regulations governing access to the drug.

As of April 1, federal authorization to possess medicinal pot for patients with chronic pain, multiple sclerosis and a variety of other ailments shifted from Health Canada to physicians.

Under the new program, doctors can provide a prescription that allows patients with symptoms that may be helped by medical pot to purchase up to 150 grams of dried weed each month from a licensed commercial grower.

Producers are subject to compliance and enforcement measures similar to those that regulate producers of other controlled substances. Licensed medical marijuana growers must meet strict security, control and reporting requirements, and are regularly inspected.

"Dried marijuana is not an approved drug or medicine in Canada. Possession and use of marijuana remains illegal unless authorized under regulations with the support of a doctor or nurse practitioner," Health Canada said.